1. Field of the Invention
This invention is generally directed to the delivery of fluids in medical procedures and, more particularly, to apparatus, systems, and methods of preventing gravitational flow of contaminated or undesirable liquids to portions of a fluid delivery system intended from multiple uses.
2. Description of Related Art
In many medical diagnostic and therapeutic procedures, a medical practitioner such as a physician injects a patient with a fluid. In recent years, a number of injector-actuated syringes and powered injectors for pressurized injection of fluids, such as contrast media (often referred to simply as “contrast”), have been developed for use in procedures such as angiography, computed tomography, ultrasound, and NMR/MRI. In general, these powered injectors are designed to deliver a preset amount of contrast at a preset flow rate.
Angiography is used in the detection and treatment of abnormalities or restrictions in blood vessels. In an angiographic procedure, a radiographic image of a vascular structure is obtained through the use of a radiographic contrast which is injected through a catheter. The vascular structures in fluid connection with the vein or artery in which the contrast is injected are filled with contrast. X-rays passing through the region of interest are absorbed by the contrast, causing a radiographic outline or image of blood vessels containing the contrast. The resulting images can be displayed on, for example, a video monitor and recorded.
In a typical angiographic procedure, the medical practitioner places a cardiac catheter into a vein or artery. The catheter is connected to either a manual or to an automatic contrast injection mechanism. A typical manual contrast injection mechanism includes a syringe in fluid connection with a catheter connection. The fluid path also includes, for example, a source of contrast, a source of flushing fluid, typically saline, and a pressure transducer to measure patient blood pressure. In a typical system, the source of contrast is connected to the fluid path via a valve, for example, a three-way stopcock. The source of saline and the pressure transducer may also be connected to the fluid path via additional valves, again such as stopcocks. The operator of the manual contrast injection mechanism controls the syringe and each of the valves to draw saline or contrast into the syringe and to inject the contrast or saline into the patient through the catheter connection. The operator of the syringe may adjust the flow rate and volume of injection by altering the force applied to the plunger of the syringe. Thus, manual sources of fluid pressure and flow used in medical applications, such as syringes and manifolds, typically require operator effort that provides feedback of the fluid pressure/flow generated to the operator. The feedback is desirable, but the operator effort often leads to fatigue. Thus, fluid pressure and flow may vary depending on the operator's strength and technique.
Automatic contrast injection mechanisms typically include a syringe connected to a powered injector having, for example, a powered linear actuator. Typically, an operator enters settings into an electronic control system of the powered injector for a fixed volume of contrast and a fixed rate of injection. In many systems, there is no interactive control between the operator and the powered injector, except to start or stop the injection. A change in flow rate in such systems occurs by stopping the machine and resetting the injection parameters. Automation of angiographic procedures using powered injectors is discussed, for example, in U.S. Pat. Nos. 5,460,609; 5,573,515; and 5,800,397.
The pressure transducers used with automatic contrast injection mechanisms and manual contrast injection mechanisms used to conduct fluid injection procedures, such as angiographic and like procedures, are extremely sensitive to even moderate pressures generated during activation of the syringe, so the operator must typically close a valve to isolate the pressure transducer from the fluid path when the syringe is activated to prevent damage to the pressure transducer. Specifically, many pressure transducers can be damaged if they are subjected to pressures as low as about 75 psi. Because even a hand-held syringe can generate pressures of 200 psi or more, the isolation of the pressure transducer is essential in order to avoid pressure transducer failure. While the syringe is not activated, the valve is usually open to monitor patient blood pressure.
In a typical automatic contrast injection mechanism, the catheter is placed in fluid communication with the injection mechanism/fluid delivery system by a fluid path set that is often made up of a single patient disposable set (“SPDS”) intended to be disposed of after a single use and a multi-use multi-patient disposable set (“MPDS”) intended to be reused for a certain number of procedures or for a given period of time. The SPDS may be 52-65 inches in length, as an example, and is usually packaged in a straight configuration. This length is acceptable for a large majority of angiographic procedures, however, there is a certain percentage of procedures that need a longer length SPDS.
The length of the SPDS is often too long for medical technicians to easily hang or store. The longer length also presents handling issues to a manufacturer, including sterilization density concerns. Prior tubing sets have been manufactured in a coiled configuration, but such a configuration is not always desirable as the tubing takes a coiled set, which makes it difficult to handle during an angiographic injection procedure because the SPDS will re-coil and pull on the catheter.
The long length or straight (or “uncoiled”) tubing in the SPDS also may present a gravitational flow situation in certain cases where blood present in the patient end of the SPDS may migrate up the tube set towards the MPDS when the SPDS is held in a vertical position. Such a vertical position is not typical during a procedure as the SPDS usually lies on the patient's legs in a horizontal position. In a small percentage of cases, medical technicians might not disconnect the SPDS form the MPDS after a procedure, but rather may let the SPDS hang down or hang up on an IV pole in a vertical position as they are taking care of the patient. This vertical position can cause a gravitational flow to initiate in the SPDS.
A gravitational flow is a fluid flow that takes place when two fluids of different densities come into contact. The denser or heavier fluid will seek to find the lowest position within a tube. If the heavier fluid is not at the lowest position, it will displace a less dense fluid and initiate a gravitational flow. This gravitational flow result can take place in several situations. In a first situation, gravitational flow can result when the SPDS tubing is left hanging down after a procedure. The higher density contrast fluid is located higher in the SPDS towards the MPDS and the lower density blood is located at the patient end of the SPDS. The denser contrast seeks to replace the lower density blood. This blood then flows up and into the MPDS contrast side if not caught in time by the user. The user at this point has to replace the contaminated MPDS. If not, blood or other contaminants in the MPDS could be injected through a new SPDS into the next patient.
A second exemplary situation can occur when a medical technician hangs the SPDS up on an IV pole after a procedure. The heavier density and blood contaminated contrast is at the patient end of the SPDS and the lighter density saline is located lower in the SPDS towards the MPDS. The denser, blood-contaminated contrast seeks to replace the lower density saline. This blood contaminated contrast then flows up and to the MPDS if not caught in time by the user. The user at this point has to again replace the contaminated MPDS.